1. Field of the Invention
The present invention relates to a technology for retrieving information on a network.
2. Description of the Related Art
Various techniques are available for retrieving desired documents. In one such technique, documents are registered as database in a personal computer (PC), and when a character string is input by a user via a keyword digital data relevant to the keyword is retrieved from the database.
For example, a document retrieval device disclosed in Japanese Patent Application Laid-open No. 2000-231568 acquires a plurality of schedule information, which is managed separate from documents subjected to be retrieved, and displays the acquired schedule information on a display screen. When one of the displayed schedule information is selected by a user, the document retrieval device extracts a character string as a keyword from the selected schedule information, and retrieves a digital document relevant to the extracted keyword from the documents subjected to be retrieved.
As described above, the document retrieval device disclosed in Japanese Patent Application Laid-open No. 2000-231568 can handle only digital documents. However, a majority of information existing in the actual world is not digital information but paper-based information such as a newspaper and a magazine. In other words, the document retrieval device disclosed in Japanese Patent Application Laid-open No. 2000-231568 cannot handle the majority of the information existing in the actual world.